Biological sciences

The size, plumage and sexual dimorphism of the endemic hairy woodpecker subspecies (Picoides villosus picoideus) were described. The findings were compared with those from parallel analyses on the coast subspecies P. v. harrisi from Vancouver Island, British Columbia. The study showed that ecological release was not the main factor in the enhanced sexual difference in the zie of P. v. picoideus fronm the Queen Charlotte Islands because sexual dimorphism in size is similar in P. v. picoideus, P. v. harrisi and continetal populations.

Utility of wing length, tail length and tail barring in determining the sex of Barred Owls collected in Michigan and Minnesota

Article Abstract:

A study was conducted to analyze the usefulness of total tail bars and wing and tail length in determining the sex of Barred Owls (Strix varia). Discriminant analysis was performed using wing and tail lengths of male and female Barred Owls in Michigan and Minnesota. The study showed important variations in wing and tail lengths of the two sexes. No differences in the number of complete tail bars between the sexes were detected. The sex of 45 out of a total of 61 owls was correctly determined using wing and tail measurements.

A study was conducted on the effects of nest stage, sex, nest type and predator location on the nest defense behavior of Eastern Screech-owls. Results showed that the owls defended their nests more intensely during the nestling stage than during the incubation stage, supporting hypotheses on age-investment and positive-reinforcement. Male owls were observed to be more vigorous in nest defense than females and responded with greater intensity as the predator approached.